GBA1 and Parkinson disease: We bilaterally injected de novo assembled αsyn-PFFs into the granule cell layer (GL) of the olfactory bulb (OB) of GBA1 D409V KI mice, and separately injected PFFs seeded by pathologic αsyn isolated from brain homogenates from patients with GBA and idiopathic (i.e., without known genetic cause) PD (GBA-PFFs and idiopathic PD-PFFs, respectively) into the OB of WT mice (See Fig. 1 for summary).